# metaclass是创建类，所以必须从'type'类型派生：
class ListMetaclass(type):
	def __new__(cls, name, bases, attrs):
		attrs['add'] = lambda self, value: self.append(value)
		return type.__new__(cls, name, bases, attrs)

	# 指示使用ListMetaclass来定制类
class MyList(list, metaclass=ListMetaclass):
		pass

L = MyList()
L.add(1)
L.add(2)
L.add(3)
L.add('END')
print(L)
			
